Process for catalytic semihydrogenation of tertiary acetylenic monohydric alcohols



Patented July 25, 195i PROCESS. FOR. CATALYTIC SEMIHYDROi- GENATION'OF TERTIARY ACETYLENIC MONOHYDRIC ALCOHOLS EycreirFcy Smith, 'llerre Haute, Ind, assignor to Commercial-Solvents Corporation, Terre Haute, 1nd,, a-corporation. of Maryland No Drawing.

Application October 4, 1945, SeriaINO. 620,407.

' z clainis. (01. 260-642) The present invention relates to a method for the preparation of: tertiary olefinic monohydric alcohols. More particularly, it pertainseto a. process for producing such alcoholsby the selective catalytic hydrogenation of the corresponding acetylenic alcohols. e

This application a continuation-in-part of my application, Serial No. 498,733,. filed. August 14, 194-3, and now abandoned.

Numerous applications have been found'for olefim'c alcohols either as such, or as intermediates in the synthesis of otherxorganic com.- pounds. For example, 2-methyl:-3.-butene-2-ol may be dehydrated to isoprene, which may. in turn be polymerized undenvarious conditions to produce several different types of rubber-like products, In'the past, howeventhe olefinic alcohols have been seriously limitedin useL because of the difliculty of producing them The most readily availahle raw materials for the productionof olefinic alcoholsare thefcorresponding. acetylenic alcohols, which; are}. prepared by condensing. aldehydesand ketones with acetylenic hydrocarbonshaving an unreplaced hydrogen atom. in the '1-.-positi0n.' Such, acetyl'enic alcohols have. been. reduced chemically. to'the olee finic alcohols-,, but the process is both expensive and inconvenient.

I- have, now discovered. that. tertiary olefinic monohydric alcohols may be consistently produced in yields of 90 per cent and above by the selective catalytic hydrogenation of the corresponding tertiary. acetylenic alcohols in the liquid. phase over palladium catalysts-selected from the class consisting of palladium black,.pa1.+ ladium supported on. charcoalpalladium supported on alumina. In carrying. out my invention, a, charge consisting of acetylenio alcohol and. catalyst, with or without, a'solvent for the acetylenic alcohol which is,inert.under the conditions of the hydrogenation, is placed; in. 9,, hydrogenation apparatus, of conventional design, and. hydrogen is introduced. and. maintained. at a pressure ranging: from, about 15 to 500 pounds per square inch, absolute, or higher.. Throughout the hydrogenation period-,dt-is, desirable to agie tate the reaction mixture by any convenient means. The hydrogenation is preferably continued until substantially all of they acetylenic alcohol has been hydrogenated. This point. may; be ascertained by. periodically withdrawing samples from the hydrogenation chamber and: testing the hydrogenated liquid by; known. methods:- for the presence of: compoundsqcontaining; an. acetylenic linkage; For examplealcohols; containing, {an

unreplaced acetylenic hydrogenatom are known toproduce a white precipitate with ammoniacal silver nitrate, Whereas the corresponding olefinic alcohols do not react in suchmanner. After-the hydrogenation has been carried to the desired point, the hydrogenated liquid; is removed from the apparatus; and the; desired olefinic alcohol is isolated in a known manner, such" as by distillation or crystallization; If desired, the ole"- finic alcohol content of the crude hydrogenated liquid maybe readily determined by rapid titration with a standard'solution of'hromine. Such analysis is based upon the fact that bromine is rapidlyand quantitatively absorbed by the olehave also observed that these palladium catalysts have an exceptionally long'life, and may be used numerous times in the-semihydrogenationof ter tiary' acetylenic alcoholsbefore their activity is appreciably impaired.

The proportion of catalyst required varies accordingto the type of catalystused, but ordi narily lies within the range of about 0.01 to 5.0 per cent, based upon the weight of aeetylenic alcohol present'. r 1 l I The temperature utilized will be found to vary widely, depending upon a numberof' processvar-ie ables, such as the type oicatalyst, the proportion of catalyst, the hydrogen: pressure, and 'the efiectiveness of agitation. I find', in'general'; that with my palladium catalysts, temperatures from about 0 to C; may be used, and that optimum. results.- areobtained in the: range 40? to 60 C. a

Although tertiary acetylenic monohyd'ric alco. hols may be. selectively: hydrogenated in: accords ance with my invention to the; corresponding, ole.- finic; alcoholsin the absence: of water or other the hydrogenationqof a mixture: of acetylenic allcqholand water; containingepproximately 5.0%

uct by known methods revealed that the olefinic alcohol, 2-methyl-3-butene-2-ol, had been produced in 91% yield, based on the acetylenic alcohol utilized.

. v m le I A'mixture of 83.0 gramsb'r 2 -methyl 3 butyne- 2-01, 190 ml. of water, and 1.4 grams of 5% pal- ,,ladium on charcoal was introduced into a suitpoint is highly desirable, in order to minimize the pyrophoric nature of the palladium catalyst The distillate, comprising olefinic alcohol," saturated alcohol, and water, may be dehydrated by suitable means, such as by azeotropic distilla tion with benzene, and the resultant anhydrous mixture may then be subjected to careful fractionation in an efficient distillation system to isolate the olefinic alcohol in substantially pure form.

.. As may be inferred from the foregoing descrip tion, my invention may be generally applied to the semihydrogenation of substantially any tertiary acetylenic monohydric alcohol to the cor responding olefinicalcohol. For illustration, the following tertiary acetylenic alcohols are mentioned as being typical of such compounds: 3,5- dimethyl l-hexyne-ii-ol, 2-methyl-3-butyne-2-ol, 3-methyl-4-pentyne-3-ol, 2-phenyl-3-butyne-2- 01 and 3-ethyl-4-pentyne-3-ol.

For the semihydrogenation of monohydric acetylenic alcohols which form an azeotrope with water, I prefer to usev a semicontinuous process carriedout in a closed system, so designed as to prevent any contact of the catalyst with the atmosphere. The use of ,a, closed system is especially desirable with palladium catalyst, in order to reduce fire hazard and mechanical losses. Briefly, the application of semicontinuous methods to my invention may be carried out by introducing. into a suitablehydrogenation apparatus a charge consisting of the acetylenic alcohol,

water, and the catalyst, in the desired proportions. Hydrogen is then introduced under the conditions previously described, preferably until substantially all of the acetylenic alcohol has been reduced, as determined by the procedure referred to above. The resultant mixture, without removal of the catalyst, is then transferred through a suitable conduit to a still, by the use of a pump or any other convenient means, where the olefinic and saturated alcohols are distilled oil in the form of azeotropes with water, leaving residual water and catalyst in the still kettle. A fresh charge of acetylenic alcohol is then introduced, together with a quantity of water equal to the. amount distilled out with the odefinic alcohol, and the mixture-is pumped back to the hydrogenation-unitfor the succeeding cycle.

My inventionmay be more specifically illustrated by the following examples:

" Example I I Amixture of 82.0 grams of 2-methyl-3-butyne- 2-01, 190 ml. of water, and 0.350 gram of palladium black was introduced into a suitable hydrogenation unit and subjected to hydrogenation at a pressure of 50 pounds per square inch, gage, and at a temperature of- C. After 1.08 moles of hydrogenhad been'abso'rbed per mole of acetylenic alcohol charged, the hydrogenation was discontinued, and thereactio'n' product was re moved from the-autoclave. Analysis of the prodable hydrogenation unit and subjected to hydrogenation at a pressure of 50 pounds per square inch, gage, and'at a temperature of 15 C. After 1.06 moles of hydrogen had been absorbed per mole of acetylenic alcohol charged, the hydrogenationwas discontinued, and the reaction prodof the product by known methods showed that uct was removed from the autoclave. Analysis theolefinic alcohol had been produced in 93% I yield, based on the acetylenic alcohol utilized.

Example III A mixture of 82.3-grams of 2-methyl-3-butyne- 2-01, 190 ml. ofwater, and 1.4 grams of 5% palladium on aluminawas introduced into asuitable hydrogenationiunit and subjected to hy-. drogenation at a pressure of 50 pounds per square inch, gage, and at a temperature of 15 C. After 1.07 moles of hydrogen had been absorbed per mole of acetylenic alcohol charged, the hydrogenation was discontinued, and the reaction product .was removed iromthej autoclave. Analysis of the product by known methods showed that the olefinicalcohol had been produced in 94% yield,-based on the acetylenic alcohol'uti lized.

i i Example IV A mixture of 355 parts of 3,5-dimethyl-1-hexyne-3-ol, 300 parts of methanol, and 2 parts of 5% palladium on charcoal-was placed in a suitable hydrogenation unitand subjected to hydro genation ata pressure of 50 pounds per square inch, gage, and at a temperature of 18 C. When tests indicated the total disappearance of acetylenic alcohol, the hydrogenation was disc'on tinned, the"redu'ction mixture was'filtered and fractionated/and a liquid boiling between 146 and 152 C. was isolated and identified as 3,5- dimethyl-l-hexene-iv-ol by bromine" titration; The yield of olefinic. alcohol was calculated to be 98% of theoretical, based on the quantity, of 3,5- dimethyl-Lhxyne-S-olutilized. 1

. 7 Example V A mixture consisting of 300'parts of 2-methyl 3-butyne- 2-ol,{ 300 parts of water, and 2 parts'of 5% palladium 'on icharcoalwas placed in an autoclave', and the autoclave was sealed. Hydrogen was then introduced to a pressure of 50 pounds per square inch, gage, and the mixture was heated to'50 C. and agitated until the last traceof 2- methyl-3-butyne-2 ol had disappeared. The hydrogenationiwas' then' stopped, the mixture was filtered and -distil led,'and"the fraction boiling around C. wasdried by 'azeotropic distillation with benzene. 'Analysis of the anhydrous distillate indicated that the olefinic alcoholhad been produced in 90% yield.-

Ewample VI Into a suitable hydrogenation unit Was introduced a mixture consistingofparts of -2'- methyl-3-buty'ne-2-ol, 5'60 parts of water, and..2 parts of 5% palladium on charcoaL- This mixture was'hydrogenatedata pressure of 50poundsper square inch, gage'g -andata temperature of 18 C. When all of' the acetylenic 1 alcohol had disappeared, the hydrogenation was stopped, the crude product was pumped to a still kettle, and the mixture was distilled through an efllcient fractionating column up to a. vapor temperature of 96 C. The distillate was dried by azeotropic distillation with benzene, and then carefully refractionated to isolate the olefinic alcohol. The still residue was measured, a new charge of 2-methyl- 3-butyne-2-ol and the proper quantity of makeup water were added, and the mixture was then pumped from the still kettle to the hydrogenation unit for the succeeding cycle.

It is to be specifically understood that the above series of examples are merely illustrative, and are to be in no way construed as limiting my invention. Broadly, my invention resides in the dis? covery that tertiary monohydric acetylenic alco- -i hols, in general, may be reduced in high yields to the corresponding olefinic alcohols, by the utilization of palladium catalysts. In general, it

may be said that the use of an equivalents or,

modifications of procedure which would normallyoccur to one skilled in the art, is included in the scope of my invention.

Having now described my invention, I claim:'

1. A process for the semicontinuous production of tertiary olefinic monohydric alcohols from the corresponding acetylenic alcohols which comprises subjecting to partial hydrogenation an aqueous solution of a tertiary monohydric acetylem'c alcohol which forms an azeotrope with water, in the presence of a. selective hydrogenation catalyst chosen from the group consisting of palladium black, palladium supported on charcoal, and palladium supported on alumina, at a temperature within the range of about 0 to 100 C. and at a hydrogen pressure within the range of about 15 to 500 pounds per square inch ab solute, transferring the entire resultant hydrogenated mixture in a closed system from the hy- REFERENCES CITED The following'references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,300,598 Schnabel Nov. 8, 1942 2,333,216 Trieschmann Nov. 2, 1943 FOREIGN PATENTS Number Country Date 288,271 Germany Oct. 3, 1915 OTHER REFERENCES Chemical Abstracts, vol. 28, pages 1669-70 (1934). Abstract of article by Zalkind, Vishyakov and Morev from Journal of General Chemistry (U. S. S. R.), vol. 3, pages 91-113 (1933). 

1. A PROCESS FOR THE SEMICONTINUOUS PRODUCTION OF TERTIARY OLEFINIC MONOHYDRIC ALCOHOLS FROM THE CORRESPONDING ACETYLENIC ALCOHOLS WHICH COMPRISES SYBJECTING TO A PARTIAL HYDROGENATION AN AQUEOUS SOLUTION OF A TERTIARY MONOHYDRIC ACETYLENIC ALCOHOL WHICH FORMS AN AZEOTROPE WITH WATER, IN THE PRESENCE OF A SELECTIVE HYDROGENATION CATALYST CHOSEN FROM THE GROUP CONSISTING OF PALLADIUM BLACK, PALLADIUM SUPPORTED ON CHARCOAL, AND PALLADIUM SUPPORTED ON ALUMINA, AT A TEMPERATURE WITHIN THE RANGE OF ABOUT 0* TO 100* C. AND AT A HYDROGEN PRESSURE WITHIN THE RANGE OF ABOUT 15 TO 500 POUNDS PER SQUARE INCH ABSOLUTE, TRANSFERRING THE ENTIRE RESULTANT HYDROGENATED MIXTURE IN A CLOSED SYSTEM FROM THE HYDROGENATED UNIT TO A STILL KETTLE WITHOUT CONTACT WITH THE ATMOSPHERE, REMOVING THE DESIRED OLEFINIC ALCOHOL FROM THE LATTER BY DISTILLATION AS THE WATER AZEOTROPE LEAVING RESIDUAL WATER AND CATALYST IN THE STILL, ADDING ACETYLENIC ALCOHOL AND ADDTIONAL WATER TO THE STILL RESIDUE, AND THEREAFTER TRANSFERRING THE RESULTANT MIXTURE INCLUDING THE ATALYST IN A CLOSED SYSTEM TO THE HYDROGENATION UNIT FOR THE SUCCEEDING CYCLE. 